Computer integrated manufacturing systems are widely used in state of the art manufacturing operations for controlling the operation of many manufacturing or production machines in one or more manufacturing plants. The machines may be organized into production lines each of which may produce a particular product. The machines in a production line may be functionally interconnected so that if one machine is unavailable due to a failure or due to maintenance activity, the entire production line may be unavailable for production, or the production capacity of the line may be limited. Computer integrated manufacturing systems may be used to control the production machines and the flow of materials from one machine to another during the course of producing a product. Computer integrated manufacturing systems may also be used to schedule the purchasing of raw materials necessary for producing a product, and for developing a master schedule for all the machines in order to produce the desired amount of product at each production line at the desired time.
In order to increase the production efficiency and manufacturing flexibility of large manufacturing operations, computer integrated manufacturing systems are now being widely installed and used. Representative computer integrated manufacturing systems are described in U.S. Pat. Nos. 4,346,446 to Erbstein et al. entitled "Management and Analysis System for Web Machines and the Like"; 4,472,783 to Johnstone et al. entitled "Flexible Manufacturing System"; 4,457,772 to Haynes et al. entitled "Management Control System for Forming Glassware"; and 4,803,634 to Ohno et al. entitled "Production Process Control System in Newspaper Printing".
A computer integrated manufacturing system which includes multiple levels of computer control to organize and disseminate the information for controlling shop floor level systems is described in U.S. Pat. No. 4,827,423 to Beasley et al. entitled "Computer Integrated Manufacturing System", assigned to the assignee of the present invention, the disclosure of which is hereby expressly incorporated herein by reference. In Beasley et al., manufacturing scheduling data and data relating to process, product and material specifications as well as bills of material are generated in an upper level computer system and refined and downloaded as needed to lower level computers controlling the shop floor process. The upper level computers are capable of communication with the computers on the lower levels, and computers on the same level are capable of communication with each other as needed to pass information back and forth.
The art has heretofore suggested adding a maintenance module to a computer integrated manufacturing system in order to integrate maintenance of the production machines into the computer integrated manufacturing system. For example, the Haynes et al. '772 patent noted above discloses a glassware production control system which also provides maintenance information. The Ohno et al. '634 patent noted above also describes a production process control computer which includes a materials and maintenance control subsystem. The materials and maintenance control subsystem controls the timing of parts replacement. The timing of parts replacement is calculated in advance from the cumulative total of the predicted life of consumable parts and operation time and displayed or printed so as to enable order placement for parts. The maintenance system includes a parts list file containing a list of all consumable parts in the system. The parts list file is updated by collecting information on the operation of the machine so that residual service lives of consumable parts may be calculated. When parts replacement is needed, the quantity of parts used for replacement is deducted from the stock volume in the parts inventory file. When the stock volume of parts in the parts inventory file becomes smaller than at the time of parts ordering, an order form slip is printed. In other words, a "point of ordering" system is provided. A running total of elapsed time is computed and compared with the durable life of parts so that the time and date of actual replacement can be calculated and a schedule of maintenance may thereby be derived.
The art has recognized the potential advantage of providing a computer integrated maintenance system for a computer integrated manufacturing system. Indeed, for a sophisticated computer integrated manufacturing system, which controls many production machines in many production lines in one or more plants, it is almost essential that maintenance be controlled and scheduled by computer. Unfortunately, heretofore known computer integrated maintenance systems did not intelligently integrate maintenance into manufacturing. For example, in presently available computer integrated maintenance systems, the computer may schedule a low priority maintenance operation such as an oil change for one machine in a production line even though a major maintenance operation for the production line may be taking place a week later. Similarly, a "point of ordering" system for spare parts may order new parts when the number in inventory falls below the number stored in the system, even though in reality the machine is scheduled to be replaced in the near future. Similarly, a computer integrated maintenance system may prescribe a number of maintenance operations to be performed at one time even though insufficient manpower exists for performing all of that maintenance at that time.
Accordingly, there is a need for an "intelligent" computer integrated maintenance system which does more than merely schedule maintenance by adding total accumulated hours and scheduling maintenance when the hours reach a predetermined number. An intelligent maintenance system must also do more than merely function as a point of order system to order maintenance parts when inventory falls below a predetermined number.
The need for an intelligent computer integrated maintenance system has become more pressing as the complexity of computer integrated manufacturing systems has increased. As the number of machines being controlled and the number of simultaneous manufacturing lines being controlled increases, it becomes difficult for a human to understand the overall work flow in sufficient detail to intelligently modify maintenance instructions generated by a computer integrated maintenance system. Similarly, it is difficult for humans to assimilate all of the maintenance data and intelligently modify spare parts ordering instructions generated by a point of ordering system.